EQUITY & EFFICIENCY
In Search of METRICS
A. Kanafani, W.J. Dunlay, M.R. Ohsfeldt
Moving Metrics
NEXTOR SEMINAR
January 29, 2004
Asilomar, California
Framework for Assessing Equity
Investment
by Agent
Returns
to Agent
Airline
Airline
Impacts
Airport
Pax.
Deployment
Metrics
Airport
Pass.
Gov.
Gov.
Others
Others
Redistribution
Two Equity issues
• Equity in A Queue.
–
–
–
–
Inherent Distribution of Delay in a Queue
Equity Effects of Queue Management Efficiency
Intra- and Inter-Airline Impacts
Unit Costs to different type of users
• Differential Impacts of System Investment
Bad Day at EWR May 24, 1999
Equity in Queues
d2
fifo
o
o
scrambled
d1
Measuring Queue Disruption
#
#
d2
d2
h
d1
s
t
t
s
d1
h
fifo
Scrambled
h
s
d1
d2
davg c.v.
d1
d2
c.v.
R
1
2
3
4
3.5
3.5
5
2
4.1
1.17
1
3
3
5
4
8.5
6
2
10
1.18
1
0.5
3
2.5
2.75
5.5
3.5
2
5.9
1.07
Good Day at EWR
davg = 57.9
σ = 49.6
c.v. = 42.5
davg = 57.9
σ = 56.8
c.v. = 55.7
C.V. Ratio = 1.31
Bad Day at EWR
C.V. Ratio = 1.31
davg = 105.1
σ = 46.6
c.v. = 20.6
davg = 105.1
σ = 73.6
c.v. = 51.6
C.V. Ratio = 2.50
Queue Rank Correlations
The Costs Of Delay
• Account for different types of delays (where, when)
• Consider distributional effects
• Technologies may shift to whom delay occurs
• Different user types value delay differently
• Nonlinear effect of duration of delay (e.g. issue of buffer)
Case Study Using ITWS
• Queuing Analysis of departures
• Uses MIT/LL Estimates of Capacity Gain
• Simulates Queue Evolution
– Delay by Aircraft Type
– Delay by Flight Type
– Delay by Airline
• Summary by Airline:
Delay Segmentation
Table 1: Calculations for Delay to Operators
On ground –
engines off
Less than buffer*
None
More than buffer**
Crew costs
On Ground engines on
Idling aircraft
costs
Idling aircraft
costs + Crew costs
Airborne Delay
Airborne aircraft costs
Airborne aircraft costs +
Crew costs
* If the airborne time is less than the planned OAG flight schedule (minus buffer, taxi in/out
times), then saved delay is multiplied by the crew costs to counterbalance the cost of the delay
taken on the ground.
** If the delay is more than the connection time, an administrative cost is added per connecting
passenger
Unit Costs of Delay
• Assumptions
– A buffer of 10 minutes for flights longer than
50 minutes gate-to-gate
– A slack time of 20 minutes in turn-around times
– A slack time of 45 minutes for connections
– 45 minutes maximum engines-on ground delay
Unit Costs of Delay
Table 2: Value for Delay to Operators (dollars per minute)
On ground –
engines off
Less than buffer
On Ground engines on
Airborne Delay
$0
$5.36
$31.58
$22.38*
$27.74
$53.96
More than buffer
*Also used for Taxi delay greater than 45 minutes and the crew time savings when the aircraft
flies faster than expected.
Based on data from the Air Transport Association Website, “System Capacity: Part II – Cost of
ATC System Delays” http://www.air-transport.org/public/industry/display1.asp?nid=5773, July
24, 2003.
TOTAL Delay Costs May 24, 1999 - EWR
$400,000
$350,000
$300,000
$250,000
With ITWS
Without ITWS
$200,000
$150,000
$100,000
$50,000
$'AA'
'CO'
'DL'
'HP'
'NW'
'TW'
'UA'
'US'
Average Delay Cost per Flight - May 24, 1999 - EWR
$3,500
$3,000
$2,500
$2,000
With ITWS
Without ITWS
$1,500
$1,000
$500
$'AA'
'CO'
'DL'
'HP'
'NW'
'TW'
'UA'
'US'
Delays Costs by Airline
3500
3000
Ave. Cost w/ Investment
2500
US
2000
DL
1500
CO
1000
NW
AA
HP
UA
TW
500
0
0
500
1000
1500
2000
Av. Cost w/o Investment
2500
3000
3500
Differentiating The Costs Of Delay
• Need to capture how the different stakeholders might value
delay, e.g.:
– Under “degraded operations”, hubbing airlines with little or no
slack or buffer times may be more adversely affected because of
delay propagation
– Under “normal operations, airlines with limited buffers will have
very little time wasted on the ground
– Technological improvements may benefits users differently